Your local school....art teacher would probably be THRILLED.
I would...but I am the music teacher...but only because i would use it up myself! or teach the children.
I am confident you will find a useful cause.

I would go with a senior center and give them the information on knitting or crocheting blankets for animal shelters. The seniors would love being able to do something useful for a good cause. Of course they could also use it to make anything else they wanted to.

If anyone has yarn that they do not want, please contact me and if there is quite a bit, I may want to have it and I would pay the shipping. I crochet more than knit, being a Nana, I am always making something. Thanks

This is an old post but since someone bumped it, I'll add don't forget about children's daycare centers. I am a teacher in daycare, and we use acrylic and cotton yarn A LOT for arts and crafts. The owners would never buy something like that so we have to depend on donations, or bring in our own if we run out.

I think seniors would appreciate it the most. They need to maintain an active lifestyle, not just for the body, but for the mind as well. Knitting, crocheting, and arts/crafts help keep their minds active and creative.